diff --git a/bookwyrm/activitypub/base_activity.py b/bookwyrm/activitypub/base_activity.py
index 15ca5a93..7d2796ef 100644
--- a/bookwyrm/activitypub/base_activity.py
+++ b/bookwyrm/activitypub/base_activity.py
@@ -227,7 +227,7 @@ def set_related_field(
     model_field = getattr(model, related_field_name)
     if hasattr(model_field, "activitypub_field"):
         setattr(activity, getattr(model_field, "activitypub_field"), instance.remote_id)
-    item = activity.to_model()
+    item = activity.to_model(model=model)
 
     # if the related field isn't serialized (attachments on Status), then
     # we have to set it post-creation
@@ -298,6 +298,7 @@ class Link(ActivityObject):
     mediaType: str = None
     id: str = None
     attributedTo: str = None
+    availability: str = None
     type: str = "Link"
 
     def serialize(self, **kwargs):
@@ -305,7 +306,6 @@ class Link(ActivityObject):
         omit = ("id", "type", "@context")
         return super().serialize(omit=omit)
 
-
 @dataclass(init=False)
 class Mention(Link):
     """a subtype of Link for mentioning an actor"""
diff --git a/bookwyrm/tests/views/books/test_links.py b/bookwyrm/tests/views/books/test_links.py
index 2aee5aed..d98e95da 100644
--- a/bookwyrm/tests/views/books/test_links.py
+++ b/bookwyrm/tests/views/books/test_links.py
@@ -80,6 +80,17 @@ class LinkViews(TestCase):
         activity = json.loads(mock.call_args[1]["args"][1])
         self.assertEqual(activity["type"], "Update")
         self.assertEqual(activity["object"]["type"], "Edition")
+        self.assertIsInstance(activity["object"]["fileLinks"], list)
+        self.assertEqual(
+            activity["object"]["fileLinks"][0]["href"], "https://www.example.com"
+        )
+        self.assertEqual(
+            activity["object"]["fileLinks"][0]["mediaType"], "HTML"
+        )
+        self.assertEqual(
+            activity["object"]["fileLinks"][0]["attributedTo"],
+            self.local_user.remote_id
+        )
 
         link = models.FileLink.objects.get()
         self.assertEqual(link.name, "www.example.com")